[68 P.O.S.]

Agreed, sounds like you need some more timing. Have you tried 14, or 16 as Geezer suggested? You want your vacuum advance set to manifold vacuum. How is the rest of your HEI setup? You’ll also want to setup your transition slots again on the new carb.
Edelbrock carbs are finicky with fuel pressure. In general they don’t like more than 6 psi. Edelbrock recommends a regulator set at 5.5 psi, or their Performer RPM fuel pump which puts out the correct pressure. Some people have no problems with Edelbrock carbs using a stock pump which pushes out 7-9 psi. I’m in the crowd that did have flooding issues. I went the Edelbrock fuel pump route because I needed a new fuel pump anyway.